1. Field of the Invention
The present invention relates to a contents delivery system and method, and more particularly, to a contents delivery system and method using object redirection for allowing a web server, which receives a request for an object included in a page from a client, to redirect the request such that a host server of a contents delivery network (CDN) provider transmits the corresponding contents and a global server load balancing (GSLB) switch of the contents delivery system.
2. Description of the Related Art
A web server of a contents provider (CP) generally provides a large number of contents (for example, videos, music, files, etc.) to clients. A large load is generated when the web server provides the whole or some of the contents to a plurality of clients one to one because the plurality of clients exist in a plurality of Internet service providers (ISPs) while the web server is connected to a single ISP.
Accordingly, traffic between ISPs exponentially increases as the number of contents providers and clients increase, and thus transmission delay and/or transmission failure rate due to traffic congestion increase. Web server fail-over may occur in the worst case.
To solve this problem, a contents delivery network (CDN) is introduced. The CDN is a service which previously stores contents converging on a web server of a contents provider located at a great distance from clients, for example, contents with large capacity, such as pictures, banners, videos or audio, or contents frequently requested by clients, in host servers globally deployed at points of presence (PoP) of a plurality of ISPs and redirects the path of the host server closest to a client when the client requests the contents provider to provide contents such that the client accesses the host server through the redirected path to be provided with the contents. Here, the host server may be referred to as a cache server, a replica server or a ghost server.
The CDN is classified into an overlay type and a network type according to system configuration. In the overlay type CDN, a server for a special purpose and a plurality of cache servers manage distribution of contents. The overlay type CDN has an advantage of simple administration because there is no need for a CDN provider to control network lower layer. In the network type CDN, network components such as a router and a switch include codes for confirming a specific application type and forwarding requests of clients according to a predetermined policy.
Recently, most of solutions of CDN providers have adopted mixture of the overlay and network types. An example of mixture of the two types is disclosed in U.S. Pat. No. 6,108,703 (Referred to as '703 patent hereinafter) entitled “Global hosting system”, issued to F. Thomson Lieghton et al., and assigned to MIT (Massachusetts Institute of Technology).
According to the '703 patent, a web server of a contents provider provides a page including a uniform resource locator (URL) (referred to as ‘modified URL’ hereinafter) of an embedded object, which is modified according to a special routine, in response to a request of a client. The web browser of the client loads the embedded object in order to display the page. The '703 patent identifies the modified URL through hierarchical DNS servers called a first level name server and a second level name server and returns the IP address of the optimum host server capable of providing the actual object to the client.
The '703 patent uses so-called DNS-based request routing. General DNS-based request routing has a problem that network latency according to DNS look-up time is aggravated. The '703 patent increases system complexity although it decreases network latency by constructing hierarchical DNS servers.
The above-described routine for generating the modified URL operates in the web server of the contents provider. An illustrative routine disclosed in the '703 patent is as follows.
1. Embedded object URL before modified:
www.domainname,com/frontpage.jpg
2. Embedded object URL after modified:
www.yy.zzz.net/aaaa/www.domainame.com/frontpage.jpg
Here, xxx field denotes a serial number, yy field denotes the second level name server, zzz field represents the first level name server and aaaa field represents other information (for example, fingerprint).
The modified URL includes a plurality of fields in addition to fields (yy and zzz) for achieving the DNS-based request routing in a complicated form. Furthermore, the routine for generating the modified URL must be executed and maintained by the web server of the contents provider.
However, when the contents provider replaces the solution of the CDN provider according to the '703 patent by the solution of another CDN provider, it is required to re-modify or change the modified URL applied to all pages according to the routine or recommendation of the solution of the other CDN provider. That is, flexibility in the change of the CDN solution is deteriorated.
Furthermore, URL modification according to the routine of the '703 patent increases the length of an HTML tag and the capacity of a page.
Accordingly, a method for solving the aforementioned problems is required.